System of space-discharge devices



Sept. 28, 1926.

A. W. KISHPAUGH SYSTEM OF SPACE DISCHARGE DEVICE Filed April 10 1924atented Sept. 28, 1926.

NITED sr ARTHUR W. KISHPAUGH, OF EAST ORANGE, NEW JERSEY, ASSIGNOR TOWESTERN ELECTRIC COMPANY, INCORPORATED,

NEW YORK.

OF NEW YORK, N. Y., A CORPORATION OF SYSTEM OF SPACE-DISCHARGE DEVICES.

Application filed April 10, 1924. Serial No. 105,456.

This invention relates to systems of space discharge devices and moreparticularly to method of and means for sequentially controlling thesupply of energy from a common power unit to the electrodes of threeelectrode space discharge devices.

According to present practice in carrier transmitting systems, highfrequency oscillations are produced, controlled or modified inaccordance with signals or impulses to be sent, and transmitted to adistant station. Systems of this type now generally used include, asamplifiers, modulators and oscillators, three electrode space dischargedevices.

The ordinary three element space dis charge device having a cathode, ananode and an impedance control electrode requires a source of heatingcurrent for the cathode and a source of space current. If the fullworking voltage of the space current source be applied to the electrodesof the device before the cathode is heated and if the magnitude of thespace current is large it may result in damage to or destruction of thedischarge device.

It has been heretofore proposed to provide means, whereby such devicesmay be safeguarded against high space voltages and excessive spacecurrent, by applying heating current to the cathodes of the devicesincluded in the apparatus and delaying the application of the operatingvoltage to'space path electrodes of the devices until after theircathodes have been heated to substantially operating temperature.

In such apparatus the full operating voltage of the space currentsource. is applied to the space paths of the device at t e instant therelay control device completes the circuit of the source.

One disadvantage of this method of operation resides in the fact that,for high quality transmission, the circuits associated with the devicesinclude reactances of different characteristics having appreciablevalues, with the result that there occurs in these circuits surges whichmay damage, or even destroy, the discharge devices.

The present invention provides an arrangement, whereby the energy isapplied to the electrodes of the discharge devices in proper sequenceand. its application is controlled to prevent the production of surges1n the circuits of the system.

In accordance with this invention current is supplied by a low voltagegenerator to heat the cathodes of the devices and space current issupplied by a relatively high voltage generator. These generators are smultaneously driven by a motor. A time limit relay energized from thecathode heatmg circuit serves to delay, until the cathodes havehad timeto become fully heated, the application of energizing current to thefield winding and completion of the armature circuit of the'high voltagegenerator. 7

A primary object of this invention is to control the application ofenergizing current to a space discharge device so that sur es do notoccur in the circuits associated W1th the device.

Another object is to control the application of energizing current to adischarge deyice, so that current is initially supplied to its spacepath at low voltage and gradually increased to normal value after thepath is rendered conductive.

A further object is to control the application of energizing currentfrom a common supply unit to a space discharge system without injury tothe discharge devices of the system.

The invention itself, both as to its organization and method ofoperation will best be understood by reference to the followingdescription taken in connection with the accompanying drawing in whichthe single figure shows diagrammatically a circuit arrangement which maybe employed in carry- 90 in the invention into effect.

he figure illustrates a radio telephone transmitting system in whichspeech currents supplied by the circuit 1, which may be a telephoneline, are transmitted by the transformer 2 to the amplifier 3.

Amplified speech currents are supplied to the input circuit of avariable impedance device, comprising two parallel connected spacedischarge tubes 4. The common output circuit of the tube 4 is associatedwith the space current circuit of two parallelconnected'space dischargedevices 5 having their input and output circuits coupled in feedbackrelation by the antenna circuit 6 1 5 to constitute a high frequencyoscillator.

Energizing current is supplied to the amplifier, variable impedancedevice and the oscillator by the generators 10 and 11 directconnected bya shaft 9 to a driving motor 8. A direct current motor is shown but analternating current motor may also be used. The low voltage generator 10supplies heating current to the filaments and the high voltage generator11 supplies curent to the space paths of the discharge devices 3, 4 and5.

The overload circuit breaker 12 serves to control the space currentsupply circuit for the discharge devices.

The radio transmitter is provided with a starting control circuit whichincludes the switch 13, battery 14 and electromagnetic switch or relay15. a

The low voltage generator 10 supplies current to a circuit 16, includingits field winding 17 in series with control resistances 18 and 19.

The circuit 16 is connected to the circuit 20 which includes the windingof a relay 21, the stationary contacts of a time-delay switch 22 and thearmature of the relay 15. The winding of the time-delay switch 22 isconnected to the circuit 16 by the conductors 23.

Switch 24 serves to connect the low voltage generator 10 to the filamentheating circuit 25 for the devices 3, "4 and 5. Switch 26 is adapted toconnect the high voltage generator 11 to the space paths of the devices3, 4 and 5. Switch 27 is provided for connecting the field winding 28 ofthe generator 11 to the circuit 16.

The space current circuit of the speech amplifier 3 extends from thepositive terminal of the generator 11, through the right hand blade ofswitch 26 which would be closed, circuit breaker 12, resistance 29,choke coil 30' to the anode, across the space path within the device toits cathode, conductor 31, resistance 32, conductor 33 and left handblade of switch 26 to the negative terminal of the generator 11.

The alternating current output circuit of the amplifier is coupled tothe grid-cathode circuitof the tubes 4 by the condenser 35. The coil 30,through which space current is supplied to the amplifier 3, is of highimpedance for speech frequency currents.

Space current is supplied to the variable impedance device, comprisingthe arallelconnected discharge tubes 4, an oscil ator, including thetubes 5, from the positive terminal of source 11, through righthand-contact of switch 26, circuit breaker 12, choke coils 37 and 38,coils 39 and 44, anodes of 4 and 5 across the space paths within them totheir cathodes, .heating circuit 25, conductor 31, resistance 32,conductor 33 and left hand contact of switch 26 to the negative terminalof the source 26.

The alternating output current circuit for the variable impedancedevice, consistin of tubes 4, may be traced from the are lelconnectedanodes, anti-singing cho re coils 39, coils 38 and 37 condenser 40,resistance 32, conductor 31, heating circuit 25, cathodes of the tubesand across the space paths within them to their anodes. The highimdedance of coils 37 and 38 at speech frequencies forces thealternating current of these frequencies to traverse the tubes 5.

Space current for the amplifier 3 as well as the variable impedancetubes 4 and tubes 5, and the alternating output current of the tubes 4flow through the resistance 32. The

potential drop due to the fiow of space current through 32 is impressedupon the impedance control electrodes of the devices 3 and 4 to polarizethem for a purpose now well understood.

The alternating output current flowing through res stance 32 sets up analternating potential drop thereacross which would be impressed upon theinput circuit of amplifier 3 and tend to interfere with its properoperation. To prevent this the polarizing potential is suppl ed througha resistance 41 which cooperate. with the condensers 36 to constitute afilter adapted to substantially absorb or suppress the interferinalternating potential developed in the resistance 32.

' Space current is supplied to the oscillating tubes 5 by generator 11over a path similar to that for tubes 4 to the upper terminal of coil38. From this point it is transmitted through the radio frequency choke42, coil 43, anttsinging choke coils 44, anodes of tubes 5, across thespace paths within them to their cathodes and thence by the same path asfor tubes 4 to the negative terminal of source 11.

The input circuit of the tubes 5 extends from their cathodes across thespace within them to their grids, coil 45 and leak path 46, including acondenser shunted by a resistance, to their cathodes.

The output coil 43 is coupled to the input coil 45 by the antennacircuit 6, which includes a variometer, whereby energy is fed back tocause the production of high frequency oscillations. The variometer isprovided to permit the constants of the antenna circuit to be adjusted,whereby the frequency of the oscillations generated may be adjusted.

A variable condenser 47, included in the output circuit of theoscillator is used to efl'ect reactance adjustments of this circuit. Thealternating output current circuit of the oscillating tubes is completedthrough the condenser 48.

The operation of the transmitter described above may be described asfollows. S eech current supplied by the circuit 1, after eing amplified,is impressed upon the common input circuit of the tubes 4 to control thearmatures.

eonora tlow of space current within them and thereby control the spacecurrent flow within the oscillating tubes 5. with the result that thehigh frequency oscillations produced by the latter have their amplitudesmodulated in accordance with the speech currents.

This arrangement utilizes the principles of the constant currentmodulation system described in Patent No. 1,442,147, January 16, 1923,to Heisinq. to which reference may be made for a complete description ofits method of operation.

The operation of the control mechanism in starting up the transmittermay now be explained. With the motor 8 operating, the switch 13 will beclosed to energize the relay 15 which pulls up its armature to close onebreak in the circuit 20. However this circuit is not completed, becausethe contacts of switch 22 are not in engagement.

The switches 24, 26. 27 and circuit breaker 12 are then closed. Thefield circuit 17 of the generator 10, including the resistance 18 and19, will be completed, but the field circuit 0. the generator 11 will beopen at the right hand contact of relay 21. Current will be suppliedfrom generator 10 through switch 24 to the filaments of the devices 3.4t and 5, to heat them, and through circuit 23 to energize the windingof the time-relay switch 22.

When the switch 22 operates to close its contacts, circuit 20 will becompleted to energize the relay 21 and pull up both of its The left handarmature will short circuit the resistance is in the field circuit ofthe generator 10, whereby the current supplied by this generator isincreased. The right hand armature completes the field circuit of thegenerator 11, which is supplied with exciting current from the generator10 through the circuit 16 and switch 27.

By providing the resistance 18, and controlling it in the mannerdescribed above, the generator 10 may be regulated to supply heatingcurrent of the proper amplitude to the filaments ot the dischargedevices at all times, whet-her the generator 11 is active or not. Inthis manner overheating of'the filaments or unstable operation of thedis charge devices is prevented.

In accordance with the operation of this control arrangement. heatingcurrent supplied to the filaments of the devices is held within safelimits at all times, and the switch 22 is used to maintain the fieldwinding circuit of the high voltage generator open until the filamentsare heated to a temperature at which space current may be safelysupplied to the devices. However, when the field winding of thegenerator 11 is completed the volta e developed across its armature isinerel that due to the residual magnetism of its field. As the currentsupplied to the winding 28 increases, the field builds up and theamplitude of the space current and voltage gradually increase fromsubstantially zero to full value. Thus an appreciable interval of timeelapses between the time when the generator 11 becomes active and thetime full voltage and current are applied to the space paths of thedischarge devices.

This arrangement therefore provides means for sequentially controllingthe application of energizing currents to space discharge devices, sothat the liability of in juring or destroying them is substantiallyeliminated, and is especially; desirable for use with systems in whichsurges may develop due to the presence of reactance of relatively largemagnitude in the circuits' A- radio telephone transmitter of the typedescribed above has been used for broadcasting entertainments. Theoutput circuit, of the low frequency or speech amplifier included achoke coil the inductance of which at speech frequencies was 40 henriesand a by-pass condenser having acapacity of 2 microfarads. The outputcircuit of the 'ariable impedance device included two choke coils,connected in series the inductance of each of which at speechfrequencies was approximately 4 henries, and a bypass con= denser of 2microfarads capacity. Space current was supplied to the dischargedevices at approximately 1600 volts. Starting this transmitter bysupplying space current to the discharge devices at full voltage of thesource, 1600 volts, resulted in the production of severe surges which attimes damaged certain of the space discharge devices.

When the control method of the present invention was used to start thetransmitter described in the preceding paragraph. no troublesome surgevoltages were produced in the circuits.

While a particular arrangement and certain details have been describedwith the object of clearly and completely disclosing the nature of theinvention. it is to be understood that- .this invention is not limitedthereto, but only by the scope of the attached claims.

What is claimed is:

, 1. The method of operating a space discharge device having a cathodeand an anode, which comprises supplying heating current to the cathodeand, after a definite time interval controlled by the heating current,applying space current at substantially zero voltage to the device andgradually increasing the voltage to normal value.

2. The method of operating a system including space discharge deviceshaving a cathode and an anode, which comprises supplying heating currentto the cathodes and thereby initiating, after the cathodes are fullyheated, the supply to the devices of increases cathode and an anode,which comprises sup' plying heating current from one generator to thecathodes and thereby initiating. after" a definite interval, theoperation of the other generator, whereby current gradually increasinfrom a log to normal amplitude is supplied to the anodes of saiddevices.

4:. In combination a space discharge device including a cathode and ananode, a source for supplying heating current to said cathode, a sourcefor supplying space current to-said device and means associated withsaid heating source for controlling, at a definite interval of timeafter heating current is supplied to said cathode, said other source tosupply to said device space current gradually increasing to normalamplitude.

5. An electrical system comprising a space discharge device having acathode and an anode, generators for supplying energy thereto, a controlstation having means for controlling said generators sequentially,whereby one of said generators supplies energizing current to one of theelectrodes of said'device for a definite interval before the othergenerator becomes operative to supply gradually increasing current tothe electrodes of said device.

6. A space discharge system comprising a plurality of discharge deviceseach having a cathode and an anode, generators for supplying energizingcurrent to said devices, means for supplying current from one of saidgenerators to said cathodes and means for, after a definite interval,completing the field circuit of said other generator whereby graduallyincreasing current is supplied to the space paths of said devices.

7. A space discharge system comprising a plurality of discharge deviceseach having a. cathode and an anode, generators for supplyin energizingcurrent to said devices, one 0% said generators supplying current tosaid cathodes a time-delay switch also supplied with current by saidcathode supply generator and means controlled by said switch forcompleting the field circuit of said other generator which suppliescurrent to the space paths of said devices.

8. A space discharge system comprising a plurality of discharge deviceseach having a cathode and an anode, generators for supplying energizingcurrent to said devices, one of said generators supplying current tosaid cathodes a time-dela switch also supplied with current by saidcathode supply generator and a relay controlled by said switch forcontrolling the supply of field current to said other generator whichsupplies current to the space paths of said devices.

In witness whereof, I hereunto subscribe my name this 9th day of AprilA. D., 192%.

ARTHUR W. KISHPAUGH.

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